/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/ViewModels/HierarchyEditor/NiagaraHierarchyViewModelBase.h
Should return true if draggable. An optional message can be provided if false that will show as a slate notification.
virtual [FCanPerformActionResults](API\Plugins\NiagaraEditor\ViewModels\HierarchyEditor\FNiagaraHierarch-_6\FCanPerformActio-) CanDragInternal()